REVERE – Suffolk Downs announced plans Wednesday to open its 2009 racing season on May 2 even as elected officials debated how to pour gambling dollars into the state’s depleted treasury.The start of spring racing at the tracks comes 10 months after Suffolk Principal Richard T. Fields joined Wonderland Greyhound Park owners in announcing a tentative agreement to join forces on future plans, including efforts to attract casino gambling to the North Shore.The announcement comes a week after state Senate President Therese Murray announced she, the governor and House Speaker Robert DeLeo have agreed that a bill expanding gambling in Massachusetts would be debated in the fall. DeLeo on Tuesday stood by comments he has made in the past supporting legislation bringing slots to race tracks, including Suffolk and Wonderland.Both legislative leaders want to capture some of the $900 million that flows from Massachusetts residents to Connecticut resort casinos each year.Mayors led by Revere’s Thomas Ambrosino underscored the loss of that revenue Wednesday by calling on city and town colleagues across Massachusetts to help them pass legislation they claim will generate $400 million in gambling money from resort casinos.They support building three resort casinos and point to demic studies indicating Massachusetts residents have spent more than $10 billion since 1993 at Connecticut and Rhode Island gaming venues and that Bay State patronage there has generated more than $4 billion in tax revenues for Connecticut and Rhode Island state governments and its cities and towns.In 2008 alone, Bay Staters spent more than $920 million at the Connecticut casinos and Rhode Island slot parlors, generating $211 million in tax payments to Connecticut and Rhode Island state governments, according to the studies.Ambrosino and other mayors claim two recent public polls have indicated majority support statewide for resort casinos. A Suffolk University poll indicated Massachusetts residents support casino gaming by a 61 percent/34 percent margin while a survey of Massachusetts residents by the Center for Policy Analysis at the University of Massachusetts showed Bay State residents support the authorization of resort casinos by 57 percent/31 percent.”Each of us is well aware that most of Massachusetts’ 351 cities and towns face severe budgetary pressures likely to result in thousands of municipal employee layoffs and almost unimaginable curtailment of programs and services,” Ambrosino and fellow mayors wrote in a letter to municipal officials, adding, “Studies show that three gaming, entertainment and destination venues will generate nearly $500 million in new tax revenues, create 10,000 construction jobs and more than 20,000 casino-related jobs.”